Our studies were conducted to determine (1) the effects of cholesterol on renal proximal tubular apical brush border membrane fluidity and ion transport activity, both in renal tubular cells grown in culture, and in isolated brush border membranes; (2) the role of alterations in membrane cholesterol and phospholipid composition and membrane fluidity in adaptation of renal tubular cell phosphate transporter to acute and chronic perturbations in extracellular phosphate concentration; and (3) the role of alterations in membrane lipid composition and fluidity in the response of the renal phosphate transport to extracellular hormones. Consulting: 36 hours with Weiming Yu to help set-up new 2-photon computer and Fluorescence microscope, on site. Also installed computer hardware and software for microscope